KR101178811B1 - Fast channel change in digital video broadcast systems over dsl using redundant video streams - Google Patents

Abstract

A method and apparatus are provided for enabling channel change in a Digital Subscriber Line (DSL) system. The channel change processing unit for enabling channel change receives at least two video streams corresponding to the same program, and at least two for transmitting based on the position of the intra-coded picture in the at least two video streams. A selector 134 for selecting one of the video streams.

Description

FAST CHANNEL CHANGE IN DIGITAL VIDEO BROADCAST SYSTEMS OVER DSL USING REDUNDANT VIDEO STREAMS}

Cross-References to Related Applications

This application claims the benefit of US Provisional Patent Application No. 60 / 586,117, filed Jul. 7, 2004, which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to digital subscriber line (DSL) systems, and more particularly, to a method and apparatus for enabling fast channel change in a DSL system using parallel streams.

In commercial video on a DSL broadcast system, it is desirable to allow end users to change channels quickly. Popular video compression standards such as MPEG-2 and JVT / H.264 / MPEG AVC use intra and inter coding. For proper decoding, the decoder must decode the compressed video sequence starting with the intra-coded (I) picture, and then continue decoding the subsequent inter-coded (P and B) picture. The picture group (GOP) may include an I picture and several subsequent P and B pictures. An I picture typically requires more bits to code than a P or B picture of equivalent video quality needs in a 3 to 10 times more bit range. When the receiver first begins to receive a program on a particular channel following a channel change or initial on of the receiver, the receiver must wait until the I picture is received to begin decoding properly, which causes a delay.

In order to minimize channel change delays in digital video broadcasting systems, I pictures are frequently transmitted, eg every N pictures. For example, it is common to use N (N = 15) content for 30 frames / second (fps) in order to be able to delay the second half (of the video compression portion of this system). Since the compressed I picture is much larger than the compressed P and B pictures, this significantly increases the bit rate than would have been necessary if I pictures were inserted too frequently.

In some systems, instead of frequently sending a complete I picture, a technique called "sequential refresh" is used, where the picture portion is intra coded. Typically, all macroblocks in a picture are intra-coded at least once during the N-picture period. I pictures typically require significantly more bits to encode than P and B pictures.

In the JVT / H.264 / MPEG AVC compression standard, P and B pictures can be predicted using multiple reference pictures, including pictures before the preceding I picture. This standard identifies random access points as Independent Decoder Refreshes, or IDRs, which force the IDR to not use any reference picture before the IDR to predict the picture following the IDR. The picture may be coded using different types of slices. A picture in which all coded slices are I type may be referred to as an I picture.

The JVT / H.264 / MPEG AVC compression standard includes a tool called duplicated picture defined in the following standards:

Redundant coded picture: A coded representation of a picture or portion of a picture. The content of redundantly coded pictures shall not be used by the decoding method for bitstreams conforming to this Recommendation | International Standard. The redundant coded picture should not contain all macroblocks in the primary coded picture. Overcoded pictures do not have a normative effect on the decoding method. See also primary coded picture.

The slice header contains redundant_pic fields, the meaning of which is specific to the JVT / H.264 / MPEG AVC compression standard as follows:

 redundant_pic_cnt must be 0 for slice and slice data partitions belonging to the primary coded picture. redundant_pic_cnt must be greater than 0 for coded slices and coded slice data partitions in a redundant coded picture. When redundant_pic_cnt is not present, its value must be inferred to be zero. The value of redundant_pic_cnt must be in the range of 0 to 127, inclusive.

Slice data partition B with the same values of slice_id and redundant_pic_cnt as in slice data partition A RBSP, if the syntax element of slice data partition A RBSP indicates the presence of any syntax element of category 3 in the slice data for the slice; RBSP must exist.

Otherwise (unless the syntax element of slice data partition A RBSP indicates the presence of any syntax element of category 3 in slice data for a slice), and has the same values of slice_id and redundant_pic_cnt as in slice data partition A RBSP. There should not be any slice data partition B RBSP.

A system has been proposed in which the channel change stream is encoded and transmitted along with the normal video bitstream. The channel change stream contains a lower quality I picture transmitted at a higher frequency than the I picture in the normal bitstream. When the user tunes to a new channel, playback can begin as soon as the first I picture is received in either the normal stream or the channel change stream. The system is targeted at end-to-end broadcast systems without any upstream indication of channel changes or possibilities for storing at the midpoint in the system.

Another system in which a reduced resolution update codec is used such that prediction residuals can be coded at a lower resolution for some of the pictures coded in the sequence, while other coded pictures in the sequence are coded at full resolution. This has been proposed. However, this system does not provide any performance for improved channel change efficiency.

Another system has been proposed in which the channel change stream is encoded and transmitted with the normal bitstream over the local broadband network. These streams can be stored in DSLAM. When a user channel change request is received at the DSLAM, the channel change stream is sent over the DSL local loop for a short transition period, followed by the normal stream. If the picture coded with the channel change stream is larger than the picture coded with the corresponding normal stream, the instantaneous bandwidth requirement of the DSL local loop will be increased. This can cause problems with encoder rate control and buffer overflow / underflow at the decoder and DSLAM. This problem can be avoided by limiting the size of the picture coded into the channel change stream, which results in lower quality video during the transition period following the channel change.

These and other drawbacks and drawbacks of the prior art are addressed by the present invention with respect to a method and apparatus for enabling fast channel switching in digital subscriber line (DSL) systems using parallel streams.

According to an aspect of the present invention, in a digital subscriber line access multiplexer (DSLAM) of a digital subscriber line (DSL) system, a channel change processing unit is provided for enabling channel change. The channel change processing unit receives at least two video streams corresponding to the same program and selects one of the at least two video streams for transmission based on the position of the intra-coded picture in the at least two video streams. It includes.

According to another aspect of the present invention, a video encoder is provided for enabling channel change in a digital subscriber line (DSL) system. The video encoder comprises an encoder for coding at least two video streams corresponding to the same program such that the at least two video streams contain intra-coded pictures occurring at different locations of the at least two video streams.

According to another aspect of the present invention, a method for enabling channel change in a digital subscriber line access multiplexer (DSLAM) in a digital subscriber line (DSL) system is provided. The method comprises the steps of receiving at least two video streams corresponding to the same program, and selecting one of at least two video streams for transmission based on the position of the intra-coded picture in the at least two video streams. It includes.

According to another aspect of the present invention, an encoding method is provided for enabling channel change in a digital subscriber line (DSL) system. The method includes coding at least two video streams corresponding to the same program such that the at least two video streams contain intra-coded pictures originating at different locations of the at least two video streams.

These and other aspects, features, and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments to be read in conjunction with the accompanying drawings.

The invention can be better understood according to the following illustrative figures.

1 is a block diagram of an exemplary end-to-end structure in accordance with the principles of the present invention.

FIG. 2A illustrates an exemplary picture coding pattern for two parallel video bitstreams in accordance with the principles of the present invention. FIG.

2B illustrates an exemplary picture coding pattern in accordance with the prior art.

3 illustrates an exemplary picture coding order pattern in accordance with the principles of the present invention.

4 illustrates an exemplary method for enabling channel change in a digital subscriber line (DSL) system in accordance with the principles of the present invention.

The present invention relates to a method and apparatus for enabling fast channel switching in a digital subscriber line (DSL) system using parallel streams. DSL local loops are most bandwidth-forced links of end-to-end video across DSL systems. Advantageously, the present invention provides a method and apparatus for allowing low channel change delay while minimizing DSL local loop bandwidth. In addition, according to the present invention, the desired channel change delay can be achieved without the need for an I picture to be transmitted over the DSL local loop as frequently as it is transmitted in prior art systems.

This detailed description illustrates the principles of the invention. As such, those skilled in the art should understand that, although not explicitly described or shown herein, various devices may be devised that implement the principles of the invention that are within the spirit and scope of the invention.

All examples and conditional statements mentioned herein are for educational purposes to aid in understanding the principles of the invention and the concepts that the inventors have made in advancing the prior art, and are not limited to those specifically mentioned examples and conditions. Will be understood.

In addition, all references listing the principles, aspects, and embodiments of the present invention, as well as specific examples thereof, are intended to cover both structural and functional equivalents of the present invention. In addition, such equivalents are intended to include both currently known equivalents and future developed equivalents, that is, any elements developed that perform the same function regardless of structure.

Thus, for example, it should be understood by those skilled in the art that the block diagrams shown herein represent conceptual diagrams of exemplary circuits that implement the principles of the present invention. Similarly, any flow chart, flow diagram, state diagram, pseudocode, etc. can be substantially represented on a computer readable medium and that computer or processor is regardless of whether the computer or processor is explicitly shown. It should be understood that this represents the various processes performed by.

The functions of the various elements shown in the figures may be provided using dedicated hardware as well as hardware capable of performing software in conjunction with appropriate software. When provided by a processor, such functionality may be provided by one dedicated processor, by one shared processor, by a plurality of individual processors, some of which may be shared. In addition, the explicit use of the term "processor" or "controller" should not be construed as referring solely to hardware capable of executing software, and should not be construed as digital signal processor (DSP) hardware, read-only memory (ROM) for storing software. ), Random access memory (RAM) and non-volatile storage media may be implicitly included.

Other hardware, conventional and / or custom, may also be included. Similarly, any switch shown in the figures is merely conceptual. The function may be executed through the operation of program logic, through dedicated logic, through the interaction of program control and dedicated logic, or even manually, and a particular technique may be selected by an implementor who understands the present context specifically. Can be.

In that claim, any element expressed as a means for performing a particular function is therefore firmware that is combined with, for example, a) a combination of circuit elements that perform such a function or b) appropriate circuitry for performing such software to perform a function. It is intended to include any manner of performing such functionality, including any form of software, including microcode, and the like. The invention defined by such claims is that the functions provided by the various mentioned means are combined and brought together in the manner required by the claims. Applicant thus regards any means that can provide these functions as equivalent to the functions shown herein.

In accordance with the principles of the present invention, the desired channel change delay can be achieved without requiring an I picture to be sent across the DSL local loop as frequently as it is transmitted in prior art systems. Two or more parallel video bitstreams are generated at the encoder, each of which includes an I picture that occurs in the bitstream at different picture positions at any desired interval. The I-picture interval for one of the parallel video streams is larger than the I-picture interval of the combined bitstream. Video decoding following a channel change may begin after any I-picture of the combined bitstream. Only one of the parallel video bitstreams is transmitted across the DSL local loop at any time for a given program, so that the DSL local loop bit rate requirement is reduced by using a larger I-picture interval, while still allowing fast channel change response. do.

Referring to FIG. 1, an exemplary end-to-end structure to which the present invention is applied is generally indicated by reference numeral 100. Exemplary end-to-end structure 100 relates to an example of the present invention using two parallel video bitstreams. However, it should be understood that the present invention can be applied to any number of parallel video bitstreams. The structure 100 includes a content provider 110, a local broadband network 120, a digital subscriber line access multiplexer (DSLAM) 130, a local loop 140, and a set top box (STB) 150. The content provider 110 includes a video encoder 112 having first and second outputs in signal communication with each of the first and second inputs of the multiplexer 114. The output of the multiplexer 114 provides the output of the content provider 110, which is connected in signal communication with the local broadband network 120. The regional broadband network 120 is further connected in signal communication with a first input of the DSLAM 130.

DSLAM 130 includes a demultiplexer 132 having first and second outputs in signal communication with each of the first and second inputs of selector 134. A first input of the DSLAM 130 is connected in signal communication with an input of the demultiplexer 132, a second input of the DSLAM 130 is connected in signal communication with a third input of the selector 134, and the DSLAM 130 is connected. Is coupled in signal communication with the output of the selector 134. The third input and output of the DSLAM 130 are connected in signal communication with a local loop 140. It is to be understood that DSLAM 130 will also be referred to herein as " channel change processing unit. &Quot;

The STB 150 includes a user interface 152 and a video decoder 154. The output of STB 150 is connected in signal communication with local loop 140 and user interface 152, and the input of STB 150 is connected in signal communication with local loop 140 and video decoder 154.

Video encoder 112 generates two parallel video bitstreams. The two parallel video bitstreams are multiplexed together and communicated to the DSL Access Multiplexer (DSLAM) 130 across the local broadband network 120. For simplicity, only one program's encoder is shown in FIG. However, it should be understood that in a real system, multiple programs are supported and the elements of FIG. 1 may overlap for several supported programs. The user requests a channel change via the user interface 152 in the STB 150 to indicate the switch of the new program to be shown. This request is sent to DSLAM 130.

Due to a channel change or first turn on of the STB 150, when a playback of a particular program is requested by the user, the request is sent to the DSLAM 130 via the local loop 140. DSLAM 130 selects one of the parallel video bitstreams to send to STB 150 via DSL local loop 140.

The bandwidth requirement for the local broadband network 120 is increased in accordance with the present invention because two or more parallel video bitstreams are transmitted for each program. The bandwidth requirement for the DSL local loop 140 is reduced because fewer I pictures are transmitted over the DSL local loop 140. I pictures typically require significantly more bits than P and B pictures of the same picture quality.

Referring to FIG. 2A, an exemplary picture coding pattern for two parallel video bitstreams is indicated generally by the reference numeral 200. Referring to FIG. 2B, an exemplary picture coding pattern for a system of the prior art is generally indicated at 250. It should be understood that the example picture coding pattern 250 for the prior art system shown in FIG. 2B will have the same channel change delay as the example picture coding pattern shown in FIG. 2A. In accordance with the present invention, bitstream # 1 and stream # 2 will be transmitted via local broadband network 120. Only one of stream # 1 and stream # 2 is transmitted over DSL local loop 140 as selected by DSLAM 130. The bit rate of stream # 1 alone or of stream # 2 alone will be of lower bit rate for the same quality as the prior art stream, which means that the prior art stream contains twice the I picture of stream # 1 or stream # 2. Because. For every I picture of a stream of the prior art, either stream # 1 or stream # 2 contains an I picture at the same location.

2A illustrates a specific example, and it should be understood that other picture coding patterns and parallel video bitstream numbers may be used while maintaining the spirit of the present invention. If it is particularly advantageous for coding efficiency, for example in scene changes, it is possible that I pictures exist in two or more parallel streams at the same location. A key requirement for encoder 112 is that an I picture must be present in at least one of the parallel streams within a predetermined interval.

Each parallel video stream may be encoded to conform to any desired rate control and buffer model. Each parallel video stream representing the same program will be encoded to follow the same rate control and buffer model. When DSLAM 130 receives a request to begin transmitting a particular program, it will select one of the parallel video streams to send to STB 150. DSLAM 130 will continue to send the selected stream to STB 150 until the program stops displaying, such as when STB 150 is turned off or the channel is changed to another program. No specific support is needed in STB 150 to support this feature, and video quality does not change after channel change. There will be an initial delay when displaying video representing a newly requested channel, and after such initial delay, smooth playback in the STB 150 will cause the DSL local loop 140 from the DSLAM 130 to the STB 150. This can be achieved by transmitting the bitstream at an average bit rate. This is different from the system described above, which can store a channel change stream in a DSLAM that can be used for a maximum or lower quality channel change stream picture. In the system described above, when the highest quality channel change picture is used, higher instantaneous bandwidth over the local loop is needed for smooth playback. In such a system described above, when a lower quality channel change picture is used, the video quality decreases momentarily in video playback. In the present invention, neither higher instantaneous bandwidth or briefly reduced video quality is required over the DSL local loop 140. However, in the present invention, the bandwidth requirement for the local broadband network 120 is increased.

One example method that the DSLAM 130 can use to select one of the parallel video streams to transmit is to monitor incoming packets from each of the streams until an I picture is present in one of the streams. DSLAM 130 may then select the stream containing the I picture to be sent to STB 150, and may continue to transmit this selected stream. The fields in the packet header may be set to indicate that the packet contains an I picture to simplify the operation required in DSLAM 130 to identify when the I picture has reached a particular stream. Alternatively, the position of the I picture in the parallel stream may be transmitted using some other means, such as a user data field, or may follow a fixed required pattern. If two or more of the parallel streams contain I pictures at the same picture position, any of these streams may be selected for transmission.

Bandwidth requirements for local broadband network 120 may be reduced in some cases using optional embodiments of the present invention. Referring to FIG. 3, an exemplary picture coding order pattern for an optional embodiment of the present invention is indicated generally by the reference numeral 300. When a scene change occurs in a video sequence, coding the scene change picture as an I picture rather than a P picture is typically more coding efficient. If an I picture is coded in stream # 1 prior to the schedule, for example because a scene change occurs, it is not necessary to also send the I picture and subsequent pictures in stream # 2. In that case, no coded picture needs to be transmitted for stream # 2 during the period following the scene change I picture while also maintaining the desired channel change interval in the STB 150. The stream selector in DSLAM 130 will now occasionally have to switch from stream # 2 to stream # 1 if this embodiment is used even if no channel change occurs. To simplify the operation of the selector 134 in the DSLAM 130, secondary information indicating the presence or absence of the coded picture in the parallel video stream may be transmitted as user data. Alternatively, DSLAM 130 may determine that the coded picture was present for the display time given in stream # 1 even if there is no corresponding coded picture in stream # 2.

Referring to FIG. 4, an exemplary method for enabling channel change in a digital subscriber line (DSL) system is generally indicated at 400. The start block 402 transfers control to the function block 405. The function block 405 sets the picture number (p = 0), and passes control to the function block 407. The function block 407 sets the stream number (s = 0), and passes control to a decision block 410. The decision block 410 determines whether the picture number p in the stream number s is an I (intra-coded) picture. If the picture number p in the stream number s is not an I picture, control is passed to a function block 415. otherwise. If the picture number p in the stream number s is an I picture, control is passed to a function block 430. At function block 415, stream number s is incremented by one (ie s = s + 1) and control is passed to decision block 420. Decision block 420 determines whether s is the (total) number of streams. If it is not equal to the number of streams, control passes back to function block 415. Otherwise, if s is the number of streams, control is passed to a function block 425. The function block 425 increments the picture number p by 1 (ie, p = p + 1), and passes control back to the function block 407. At function block 430, picture p is transmitted from stream s and control is passed to function block 435. The function block 435 increments the picture number p by 1 (ie, p = p + 1), and passes control to a decision block 440. Decision block 440 determines whether a "shutdown request" has been received (ie, the user has turned off set top box 150). If no termination request has been received, control is passed to a decision block 445. Otherwise, if an end request has been received, control is passed to an end block 450. At decision block 445, it is determined whether a channel change request has been received. If a channel change request has been received, control is passed back to decision block 410. Otherwise, if a channel change request has not been received, control passes to decision block 460. Decision block 460 determines whether picture p is present in stream s. If the picture p is in the stream s, control is passed back to the function block 430. Otherwise, if p is not present in the stream s, control is passed back to the function block 407.

Some of the many additional advantages / characteristics of the present invention will now be described. For example, one advantage / feature is a channel change processing unit in DSLAM that receives two or more video streams corresponding to the same program and selects one of the streams to transmit based on the location of the intra-coded picture within the stream. Another advantage / characteristic is the channel change processing unit as described above, where the presence of an intra-coded picture is determined by a field in the packet header. In addition, another advantage / characteristic is the channel change processing unit as described above, wherein the position of the intra-coded image follows a predetermined pattern. Another advantage / feature is a video encoder that generates two or more video bitstreams representing the same program, which include intra-coded pictures that occur at different locations in separate video bitstreams. Yet another advantage / feature is an encoder as described above, wherein the maximum spacing between intra-coded pictures of the combined video bitstream is limited based on the desired channel change acquisition time.

These and other features and advantages of the present invention can be readily identified by those skilled in the art based on the teachings herein. It should be understood that the teachings of the present invention may be implemented in various forms of hardware, software, firmware, special purpose processors, or a combination thereof.

More preferably, the lessons of the invention are implemented in a combination of hardware and software. In addition, the software is preferably implemented as an application program that is explicitly implemented in the program storage unit. The application program can be uploaded to and executed by a machine containing any suitable structure. Preferably, the machine is implemented on a computer platform having hardware such as one or more central processing units (CPUs), random access memory (RAM), and input / output (I / O) interfaces. The computer platform may also include an operating system and microinstruction code. The various processes and functions described herein may be part of the microinstruction code, part of the application program, or some combination thereof that may be performed by the CPU. In addition, several other peripheral units can be connected to computer platforms such as additional data storage units and printing units.

Since some of the method and component system components described in the accompanying drawings are preferably implemented in software, the actual connection between the system components or processor functional blocks may further differ depending on how the invention is programmed. You have to understand. Given the teachings herein, one of ordinary skill in the art would be able to contemplate these and similar implementations or configurations of the present invention.

Although the exemplary embodiments have been described herein with reference to the accompanying drawings, the invention is not limited to these precise embodiments, and various changes and modifications can be realized by those skilled in the art without departing from the spirit and scope of the invention. Understand that there is. All such changes and modifications will be included within the scope of the invention as set forth in the appended claims.

As described above, the present invention is used in a digital subscriber line system, and more particularly, in a method and apparatus for enabling fast channel change in a DSL system using parallel streams.

Claims (21)

A selector 134 for receiving at least two video streams corresponding to the same program and for selecting one of the at least two video streams for transmission based on the position of the intra-coded picture within the at least two video streams. A channel change processing unit for enabling channel change, The scene change is coded in only one of at least two video streams, not coded in another of at least two video streams, and the selector 134 is coded in only one of at least two video streams. Switching from any other of the at least two video streams to only one of the at least two video streams based on the presence of a scene change, so that only one of the at least two video streams even in the absence of a channel change request Sent, Channel change processing unit 2. The channel change processing unit of claim 1, wherein the selector (134) uses a field in a packet header of at least two video streams to determine the presence of an intra-coded picture. The channel change processing unit of claim 1, wherein the position of the intra-coded picture in the at least two video streams follows a predetermined pattern. 2. The channel change processing unit of claim 1, wherein the selector (134) is further for receiving a channel change request, wherein one of the at least two video streams is selected for transmission in response to receiving the channel change request. delete As a video encoder that allows for quick channel changes, An encoder 112 for coding at least two video streams corresponding to the same program such that the at least two video streams include intra-coded pictures originating at different locations within the at least two video streams, The encoder 112 codes a scene change as an intra-coded picture in only one of the at least two video streams and is not coded in the other of the at least two video streams so that in subsequent transmission of the at least two video streams. Reducing bandwidth consumption on Video encoder. 7. The video encoder of claim 6, wherein the maximum spacing between intra-coded pictures of a combination of at least two video streams is limited based on a desired channel change acquisition time. 7. The video encoder of claim 6, wherein the encoders (112) each code a field in a packet header of a packet of at least two video streams, wherein the field is for indicating the presence of an intra-coded picture. 7. The video encoder of claim 6, wherein the encoder (112) codes each intra-coded picture in at least two video streams such that the intra-coded picture follows a predetermined pattern. delete As a way to make channel changes, Receiving at least two video streams corresponding to the same program; Selecting one of at least two video streams for transmission based on the position of the intra-coded picture in the at least two video streams (430), The scene change is coded in only one of the at least two video streams and is not coded in another of the at least two video streams, and the method detects the presence of a coded scene change in only one of the at least two video streams. Switching from any other of the at least two video streams to only one of the at least two video streams on the basis so that only one of the at least two video streams is transmitted even in the absence of a channel change request Further comprising, How to make channel changes. 12. The method of claim 11, wherein the selecting comprises determining (410) the presence of an intra-coded picture using a field in a packet header of at least two video streams. . 12. The method of claim 11, wherein the position of the intra-coded picture in at least two video streams follows a predetermined pattern. 12. The method of claim 11, further comprising the step 445 of receiving a channel change request, wherein one of the at least two video streams is selected for transmission in response to the channel change request. Way. delete An encoding method that allows for quick channel changes. Coding at least two video streams corresponding to the same program such that the at least two video streams include intra-coded pictures originating at different locations of the at least two video streams, The coding step codes the scene change as an intra-coded picture in only one of the at least two video streams, but not in the other of the at least two video streams, upon subsequent transmission of at least two video streams. To reduce the bandwidth consumption to Encoding Method. 17. The method of claim 16, wherein the maximum spacing between intra-coded pictures of a combination of at least two video streams is limited based on a desired channel change acquisition time. 17. The method of claim 16, wherein the coding step codes each field in a packet header of a packet of at least two video streams, wherein the field is for indicating the presence of an intra-coded picture. 17. The method of claim 16, wherein the coding step codes each intra-coded picture in at least two video streams such that the intra-coded picture follows a predetermined pattern. delete As a way to make channel changes, Generating at least two video streams corresponding to the same program; Selecting one of at least two video streams for transmission based on the position of the intra-coded picture in the at least two video streams (430), The scene change is coded in only one of the at least two video streams, and not coded in the other of the at least two video streams, and the method detects the presence of a coded scene change in only one of the at least two video streams. Switching from any other of the at least two video streams to only one of the at least two video streams on the basis so that only one of the at least two video streams is transmitted even in the absence of a channel change request Further comprising, How to make channel changes.

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